Mammillaria wrightii
Proc. Amer. Acad. Arts 3: 262. 1856.
Plants usually unbranched. Roots: upper portion of primary-root somewhat thickened and succulent proximally, otherwise fibrous. Stems flat-topped or spheric, 4–8 × 4–8 cm, ± flaccid; tubercles 6–24 mm; axils appearing naked; cortex and pith mucilaginous; latex absent. Spines 9–31 (–34) per areole, white, usually tipped brown; radial spines 8–30 per areole, in 1 series, glabrous (puberulent in first-year flowering plants); lateral spines bristlelike, 7–11 mm, stiff, longest and thickest of spines; adaxial spines often darker; central spines 1–4 (–7) per areole, porrect or strongly projecting, 1 or all hooked, (5–) 12–14 (–21) mm; subcentral spines 0. Flowers 2.5–3.5 (–5.2) × 2.2–4.5 (–7.5) cm; outer tepal margins conspicuously fringed; inner tepals rose-pink or magenta [white], margins often paler; stigma lobes yellow or pale green (rarely reddish). Fruits green or dull purple, spheric to ovoid or obovoid, (9–) 13–20 (–28) × (6–) 7–1.9 (–26) mm, juicy throughout; floral remnant persistent. Seeds black, 1.3–1.5 mm, pitted; testa hard, anticlinal cell-walls straight (not undulate); interstices conspicuously narrower than pit diameters; pits bowl-shaped. 2n = 22.
Distribution
Ariz., N.Mex., Tex., Mexico
Discussion
Varieties 3 (2 in the flora).
Key
| 1 | Radial spines usually 8-15 per areole; fruits 12.5-26 mm diam | Mammillaria wrightii var. wrightii |
| 1 | Radial spines usually 16-30 per areole; fruits 6-15 mm diam | Mammillaria wrightii var. wilcoxii |